Gaussian Process
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> Use a polynomial function of your choice, draw 40 samples from it and fit it with a Gaussian Process, then plot the
result
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<think>
The user wants me to:
1. Create a polynomial function
2. Generate 40 samples from this function
3. Add noise to make them realistic samples
4. Fit a Gaussian Process to these samples
5. Plot the result
I'll use the `gp_fit` module available to me for the Gaussian Process fitting and visualization. Let me break this down
into steps:
1. Define a polynomial function (e.g., a cubic function)
2. Generate 40 samples with added noise
3. Use the gp_fit function to fit a Gaussian Process to these samples
4. Plot the original function, the noisy samples, and the GP fit
</think>
I'll create a polynomial function, generate noisy samples from it, fit a Gaussian Process regression model, and
visualize the results. Let me implement this step by step:
╭─ Code action ────────────────────────────────────────────────────────────────────────────────────────────────────────╮
│ 1 importnumpyasnp│
│ 2 importmatplotlib.pyplotasplt│
│ 3 fromsklearn.gaussian_processimportGaussianProcessRegressor│
│ 4 fromsklearn.gaussian_process.kernelsimportRBF,ConstantKernelasC│
│ 5 │
│ 6 # 1. Define a polynomial function (cubic function)│
│ 7 deftrue_function(x):│
│ 8 return0.5*x**3-2*x**2+1.5*x+3│
│ 9 │
│10 # 2. Generate evenly spaced x values for the true function│
│11 X_true=np.linspace(-3,3,100).reshape(-1,1)│
│12 y_true=true_function(X_true.flatten())│
│13 │
│14 # 3. Generate 40 random samples with noise│
│15 np.random.seed(42)# For reproducibility│
│16 X_samples=np.random.uniform(-3,3,40).reshape(-1,1)│
│17 y_samples=true_function(X_samples.flatten())+np.random.normal(0,2,40)│
│18 │
│19 # Display the function and samples│
│20 plt.figure(figsize=(10,6))│
│21 plt.plot(X_true,y_true,'b-',label='True function')│
│22 plt.scatter(X_samples,y_samples,color='red',label='Noisy samples')│
│23 plt.title('Polynomial Function with Noisy Samples')│
│24 plt.xlabel('x')│
│25 plt.ylabel('y')│
│26 plt.legend()│
│27 plt.grid(True)│
│28 plt.show()│
│29 │
│30 print(f"Generated 40 noisy samples from a cubic polynomial: 0.5x³ - 2x² + 1.5x + 3")│
╰──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯
Accumulated token usage: input=3.48k, thinking=132, output=640, cache_write=0, cache_read=3.28k; Accumulated costs:
0.020 USD
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<Figure size 1000x600 with 1 Axes>Generated 40 noisy samples from a cubic polynomial: 0.5x³ - 2x² + 1.5x + 3
Produced images:

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Model response ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Now, I'll use the `gp_fit` module to fit a Gaussian Process regression model to the noisy samples and visualize the
result:
╭─ Code action ────────────────────────────────────────────────────────────────────────────────────────────────────────╮
│ 1 fromgp_fitimportgp_fit,plot_pred│
│ 2 │
│ 3 # 4. Fit a Gaussian Process to the samples│
│ 4 gp_results=gp_fit(X_samples,y_samples,alpha=1.0,n_restarts=10)│
│ 5 │
│ 6 # 5. Plot the results│
│ 7 fig=plot_pred(X_true,y_true,X_samples,y_samples,gp_results,│
│ 8 title='Cubic Polynomial Function Fitted with Gaussian Process')│
│ 9 plt.show()│
│10 │
│11 # Print information about the fitted model│
│12 print("Gaussian Process fit summary:")│
│13 print(f"- Kernel parameters: {gp_results['gp'].kernel_}")│
│14 print(f"- Log-likelihood: {gp_results['gp'].log_marginal_likelihood(gp_results['gp'].kernel_.theta):.2f}")│
│15 print(f"- Number of samples used: {len(X_samples)}")│
│16 print(f"- Noise parameter (alpha): {gp_results['gp'].alpha}")│
╰──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯
Accumulated token usage: input=7.76k, thinking=132, output=971, cache_write=0, cache_read=6.56k; Accumulated costs:
0.038 USD
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<Figure size 1000x600 with 1 Axes>Gaussian Process fit summary:
- Kernel parameters: 25.1**2 * RBF(length_scale=2.32)
- Log-likelihood: -113.79
- Number of samples used: 40
- Noise parameter (alpha): 1.0
Produced images:

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Model response ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
## Polynomial Function with Gaussian Process Regression
I've created a simulation where:
1. **Polynomial Function**: I used a cubic polynomial function of the form:
```
f(x) = 0.5x³ - 2x² + 1.5x + 3
```
2. **Sample Generation**: I generated 40 noisy samples from this function by adding Gaussian noise with a standard
deviation of 2.0, creating realistic "observations" that might occur when measuring a real-world phenomenon.
3. **Gaussian Process Fitting**: I then fit a Gaussian Process regression model to these noisy samples. The GP model
uses a Radial Basis Function (RBF) kernel, which is well-suited for smoothly varying functions.
4. **Visualization**:
- The blue line represents the true underlying polynomial function
- The red dots show the 40 noisy samples
- The black line is the GP model's prediction
- The gray shaded area shows the 95% confidence interval (uncertainty) of the prediction
5. **Model Details**:
- The fitted kernel has a variance of 25.1² and a length scale of 2.32
- The noise parameter (alpha) was set to 1.0
- The log-likelihood of the fitted model is -113.79
The visualization shows how the Gaussian Process provides a good approximation of the underlying polynomial function,
even with noisy samples. The confidence intervals widen in areas with fewer samples, demonstrating how GP models
naturally quantify prediction uncertainty.
This is a classic example of using Gaussian Processes for non-parametric regression, where we don't assume a specific
functional form (like a polynomial of a certain degree) but instead let the data inform the shape of the function
through the kernel.
Would you like me to modify any aspect of this demonstration, such as trying a different polynomial function or
adjusting the noise level?
Accumulated token usage: input=12.58k, thinking=132, output=1.41k, cache_write=0, cache_read=9.83k; Accumulated costs:
0.059 USD
╭─ Produced images ────────────────────────────────────────────────────────────────────────────────────────────────────╮
│workspace/images/default/9721d34c.png│
│workspace/images/default/a585cb5a.png│
╰──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯
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